Polyethylene glycol mediated, one-pot, three-component synthetic protocol for novel 3-[3-substituted-5-mercapto-1,2,4-triazol-4-yl]-spiro-(indan-1′,2-thiazolidin)-4-ones as new class of potential antimicrobial and antitubercular agents

Article abstract of DOI:10.1002/jhet.1605

A series of 3-[3-substituted-5-mercapto-1,2,4-triazol-4-yl]-spiro-(indan-1′,2-thiazolidin)-4-ones 2 were designed for the purpose of searching for novel antimicrobial agents and have been synthesized conveniently in a single step with a three-component protocol in polyethylene (400) as green reaction media. Thus, the condensation reaction between indane-1-one; 4-amino-5-mercapto-1,2,4-triazoles and mercaptoacetic acid in polyethylene glycol (400) gave quantitatively and analytically pure titled compounds 2. The structure of synthesized compound 2 is based on spectral (IR, ¹H-NMR, and ¹³C-NMR) as well elemental analyses. These compounds have been screened for their antibacterial, antifungal, and antitubercular activities. Some of them have showed significant inhibition on fungal and bacterial growth and antitubercular activity against Mycobacterium tuberculosis. The compounds 2a, 2d, and 2e display antifungal activity against Candida albicans [minimum inhibitory concentration (MIC) 3.13, 6.25 μg/mL] and antibacterial activity against Streptococcus pneumoniae (MIC 3.13 μg/mL) of the order of standard drugs tested under similar conditions, and compound 2a showed better antitubercular activity than other compounds against M. tuberculosis (H₃₇Rv strain, MIC 12.5 μg/mL).

Full text of DOI:10.1002/jhet.1605

Month 2014
Polyethylene Glycol Mediated, One-Pot, Three-Component Synthetic
Protocol for Novel 3-[3-Substituted-5-mercapto-1,2,4-triazol-4-yl]-
spiro-(indan-10,2-thiazolidin)-4-ones as New Class of Potential
Antimicrobial and Antitubercular Agents
*
Sarvesh Kumar Pandey, Akeel Ahamd, O. P. Pandey, and Nizamuddin Khan
Department of Chemistry, D. D.U. Gorakhpur University, Gorakhpur 273009, Uttar Pradesh, India
*
E-mail: prnukhan@gmail.com
Received October 18, 2011
DOI 10.1002/jhet.1605
Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
A series of 3-[3-substituted-5-mercapto-1,2,4-triazol-4-yl]-spiro-(indan-10,2-thiazolidin)-4-ones 2 were
designed for the purpose of searching for novel antimicrobial agents and have been synthesized conveniently
in a single step with a three-component protocol in polyethylene (400) as green reaction media. Thus, the
condensation reaction between indane-1-one; 4-amino-5-mercapto-1,2,4-triazoles and mercaptoacetic acid in
polyethylene glycol (400) gave quantitatively and analytically pure titled compounds 2. The structure of
synthesized compound 2 is based on spectral (IR, 1H-NMR, and 13C-NMR) as well elemental analyses. These
compounds have been screened for their antibacterial, antifungal, and antitubercular activities. Some of them
have showed significant inhibition on fungal and bacterial growth and antitubercular activity against Mycobac-
terium tuberculosis. The compounds 2a, 2d, and 2e display antifungal activity against Candida albicans
[minimum inhibitory concentration (MIC) 3.13, 6.25mg/mL] and antibacterial activity against Streptococcus
pneumoniae (MIC 3.13mg/mL) of the order of standard drugs tested under similar conditions, and compound
2a showed better antitubercular activity than other compounds against M. tuberculosis (H37Rv strain, MIC
12.5 mg/mL).
J. Heterocyclic Chem., 00, 00 (2014).
INTRODUCTION
Thiazolidinone, an important class of sulfur-containing
and nitrogen-containing heterocycles, has received exten-
sive interest in the recent past owing to their clinical use
and wide application as toxic agents in cells of pathogenic
organism [6–12]. Among them, several thiazolidinone
derivatives were designed and synthesized as antibacterial
[13], antifungal [14], anticonvulsant [15], anti-HIV [16],
and antitubercular [17] agents. Similarly, the importance
of 1,2,4-triazoles as versatile pharmacodynamic moiety has
been well documented in many of its derivatives, which
exhibited anti-inflammatory [18], antiviral [19], antimycotic
[20], and antimicrobial activities [21]. In addition, a series of
1,2,4-triazole derivatives have been patented and extensively
employed in agriculture [22].
Antibiotics are among the most prescribed drugs in the
world today. Several bacterial infections such as diarrhea,
food poisoning, and rheumatic, salmonellosis extraintestinal,
and intestinal wall infections are caused by multidrug resis-
tant Gram-positive and Gram-negative pathogens [1,2]. This
resistance of pathogenic bacteria toward available antibiotics
is rapidly becoming a major threat worldwide to human
health. In addition, the primary and opportunistic fungal
infections continue to increase dramatically because of the
growing number of immunocompromised hosts such as
AIDS patients or those undergoing anticancer chemotherapy
or transplantations [3–5]. Not only this, they also easily
gained resistance, which is the main problem encountered
in developing safe and efficient antifungal agents. Therefore,
design of new antimicrobial compounds in structural classes
to deal with these problems is of prime interest.
The union of heterocyclic rings through a spiro carbon
atom often results compounds with interesting biological
activities [23–26]. In light of these observations and continu-
ing our ongoing research on novel heterocycles [27–31] with
© 2014 HeteroCorporation

S. K. Pandey, A. Ahamd, O. P. Pandey, and K. Nizamuddin
Vol 000
biological interest, we consider it of interest to combine
aforesaid heterocyclic nuclei with indane ring [32] through
a spiro carbon atom in a single molecular framework 2
to see their additive effect toward biological activities of
titled compounds. Several groups have been substituted at
position-3 in the triazole ring to investigate the influence of
such structural variation on anticipated biological activities.
This investigation further appeared interesting because the
titled compounds 2 may serve as a very suitable ligand to
chelate essential metals present in fungi cells [33] as proposed
in Figure 1. Formation of such metal chelates will increase the
hydrophobic properties of metal ions, and this enables them
to pass through lipoid layers of cellular membrane to the
fungus cell, thereby leading to their poisoning [34].
Recently [35,36], PEG and its monomethyl ethers have
emerged as an alternative green reaction media with unique
properties such as thermal stability, commercial availability,
nonvolatility, immiscibility with a number of organic
solvents, and recyclability. On the other hand, PEGs are
inexpensive, nonhalogenated, and easily degradable and
possess low toxicity [37]. These properties of PEGs are
making them as green reaction media in organic synthesis.
Therefore, the development of facile and convenient
synthetic route to achieve rapid access to these novel
spiroheterocycles is of prime interest. Thus, in the present
investigation, the titled compounds 2 were synthesized by
one-pot, three-component green protocol and evaluated
for their antimicrobial and antitubercular activity.
experiment in which the intermediates 1a–h were isolated,
characterized, and then subjected to react with mercaptoacetic
acid under [3 + 2] annulation reaction in polyethylene glycol
to give 2a–h. Superimposable IR, 1H-NMR, 13C-NMR spec-
tra as well as mixed melting points and elemental analysis
confirmed the authenticity of the final products formed by us-
ing one-step and two-step methods. However, the reported
yield of the final products is by the use of the one-step process.
Spectral studies. The structures of Schiff bases (1aꢁh)
were identified from IR spectra, which showed absorption
bands at 1602–1576 cmꢁ1 attributed to imine (C═N), bands
at 1520–1563 cmꢁ1 attributed to C═N of the 1,2,4-triazole
nucleus, and a characteristic band at 2750–2778 cmꢁ1
attributed to -SH. The structure was further supported by
1H-NMR spectrum exhibiting signals at d 2.78–3.09 (-SH),
6.81–7.93 (aromatic H), and 1.79–2.39 (methylene H). The
13C-NMR spectrum of Schiff bases (1a–h) showed signals
at d 152.3–157.4 due to imine carbon. The signals that
appeared at d 20.3–32.4 are assigned to methylene carbon.
Signals at d 64.5–67.2 are due to -OCH2-. The aromatic
carbon appeared in the range of d 120.0–149.8.
The IR spectrum of 2a–h exhibited the absorption of new
bands at 1701–1714 cmꢁ1 attributed to the C═O group and
the appearance of peaks at 703–689 cmꢁ1 attributed to
C-S-C, which clearly indicates the formation of titled com-
1
pounds. H-NMR spectrum exhibiting new signals at d
3.63–3.91 (CH2, thiazolidinone ring) clearly supports that
the annulation took place between Schiff base and mercap-
toacetic acid to obtain the titled compounds (2a–h). Further,
13C-NMR spectrum of 2a–h is in good agreement with struc-
tures of titled compounds. In 13C-NMR spectrum, three new
signals at d 184.3–190.2 attributed to C═O carbon, at d
68.1–71.2 attributed to spirocarbon, and at d 34.6–38.5 for
CH2 of thiazolidinone ring appeared. The aromatic carbon
appeared in the range of d 121.2–149.4 ppm.
RESULTS AND DISCUSSION
Synthesis. The starting material 4-amino-3-substituted-5-
mercapto-[1,2,4]-triazoles was prepared from corresponding
acid hydrazides, CS2, and KOH as reported in literature
to obtain potassium salt, which was reacted with hydrazine
hydrate, followed by acidification with dil. HCl that afforded
the triazoles. The one-pot reaction between 4-amino-5-
mercapto-1,2,4-triazoles, indan-1-one, and mercaptoacetic
acid in polyethylene glycol at 40ꢀC yielded 2a–h (Scheme 1).
The reaction was supposed to occur via the formation of
intermediate Schiff bases (1a–h) by the condensation reac-
tion between indan-1-one and 4-amino-3-substituted-5-
mercapto-[1,2,4]-triazoles followed by [3 + 2] annulation of
mercaptoacetic acid with Schiff base to afford the corre-
sponding compounds 2a–h in quantitative yields. The
authenticity of this speculation was confirmed by an
Antimicrobial activity
Antibacterial activity. The newly synthesized compounds
(2a–h) were screened for their antibacterial activity
against Gram-positive bacteria, S. pneumoniae and Bacillus
subtilis, and Gram-negative bacteria Escherichia coli and
Pseudomonas aeruginosa, by disk diffusion method [38].
The antibacterial data (Table 1, Fig. 2.) revealed that all
tested compound of this investigation are moderately
to highly active against all the pathogenic bacteria. The
compounds 2a, 2d, and 2e were highly active against all
pathogenic bacteria, whereas the rest of the compounds
showed moderate activity as compared with the standard
drug Ciprofloxacin. The data also revealed that the activity
of compound 2a > 2e > 2d. The different substituents on
the aromatic ring exert a significance influence on the
antibacterial activity. The presence of electron donating
methyl group increases activity in general while its orien-
tation at position-2, for example, 2e worked better than at
position-4, for example, 2d. The presence of electron
Figure 1. Chelation property.
Journal of Heterocyclic Chemistry
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Spirothiazolidinones as New Class of Potential Antimicrobial and Antitubercular Agents
Scheme 1. Synthetic route for intermediate and final compounds.
withdrawing groups (halogen and nitro) on the aromatic
ring decreases the antibacterial activity as compared with
the standard drug. The most active compound was 2a,
which contains a pyridine ring in place of phenyl moiety.
This moiety is additive toward antibacterial activity in this
class of compounds. It is to be noted that compounds 2a,
2d, and 2e are more potent against Gram-positive than
Gram-negative bacteria.
Antifungal activity. Newly prepared compounds were
screened for their antifungal activity against Candida
albicans, Aspergillus fumigatus, and Aspergillus flavus
(recultured) in DMSO by serial plate dilution method [39].
The antifungal screening data (Table 1, Fig. 3) revealed
that all tested compounds showed moderate to strong
antifungal activity, but compounds 2a, 2c, 2d, 2e, and 2h
emerged as very active agents against all the tested fungal
strains. The data also revealed that the activity of
compounds 2a > 2d > 2e > 2h > 2c. On the other hand,
the nature of the substituents is critical to antifungal activ-
ity. The compounds 2c and 2h contain electron withdraw-
ing groups 2-chlorophenoxy and 2,4-dichlorophenyl
moiety, respectively, in their structures, whereas 2d and
2e contains electron donating methyl group at position-4
and position-2 on the phenyl ring. This shows that the pres-
ence of electron donating group increases the antifungal ac-
tivity as compared with electron withdrawing groups
(halogen and nitro) in this class of compounds. It is notable
that the entire tested compounds are more active on C. albi-
cans than other fungal strains. We were expecting that the
chelation behavior of the synthesized compound will in-
crease the antifungal activity, but it is not found so.
Among these, the most active compound 2a contains a
pyridine ring and showed activity, which is comparable with
the standard compound tested under similar condition. This
Journal of Heterocyclic Chemistry
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S. K. Pandey, A. Ahamd, O. P. Pandey, and K. Nizamuddin
Vol 000
Table 1
Antimicrobial and antitubercular activity of synthesized compounds.
Antibacterial activity
Antifungal activity
Antitubercular activity
Streptococcus
pneumoniae
Bacillus Escherichia Pseudomonas
Candida
albicans
Aspergillus Aspergillus Mycobacterium tuberculosis
Compound
subtilis
coli
aeruginosa
fumigatus
flavus
(H37Rv strain)
2a
2b
2c
2d
2e
2f
2g
2h
38 (3.13)
20 (12.5)
21 (12.5)
27 (3.13)
38 (3.13)
17 (50)
23 (6.25)
22 (6.25)
38 (3.13)
–
31 (12.5) 30 (6.25)
19 (25) 21 (12.5)
20 (6.25) 19 (12.5)
26 (6.25) 25 (12.5)
31 (6.25) 27 (12.5)
20 (12.5) 19 (12.5)
27 (6.25)
23 (6.25)
21 (25)
22 (12.5)
26 (25.0)
14 (50)
20 (50)
21 (12.5)
38 (3.13)
–
32 (3.13)
21 (12.5)
22 (12.5)
27 (3.13)
29 (6.25)
20 (25)
19 (25)
26 (6.25)
–
29 (12.5)
20 (25)
20 (25)
25 (6.25)
28 (12.5)
19 (25)
21 (12.5)
24 (6.25)
–
29 (6.25)
19 (12.5)
21 (12.5)
26 (12.5)
27 (25)
22 (12.5)
20 (12.5)
25 (12.5)
–
12.5
>12.5
>12.5
>12.5
>12.5
>12.5
>12.5
>12.5
–
21 (25)
20 (25)
18 (25)
20 (12.5)
Ciprofloxacin
Fluconazole
Isoniazid
(INH)
37 (6.25) 37 (3.13)
–
–
–
–
32 (3.13)
–
28 (6.25)
–
30 (6.25)
–
–
0.75
–
–
Zones of inhibition expressed in mm and minimum inhibitory concentrations (mg/mL) were given in brackets.
listed in Table 1. Biological results of the synthesized
compounds reveal that compound 2a showed a minimum
inhibitory concentration (MIC) value 12.5 mg/mL, which is
better than the other compounds. Compound 2a containing
pyridine ring in place of phenyl ring at position-3 of triazole
nucleus is highly active. This suggests that the presence of
pyridyl moiety enhances the activity against M. tuberculosis
among all the compounds tested.
In conclusion, this article reports a simple, convenient,
one-pot, three-component green synthesis of novel spiro
(indan-10,2-thiazolidin)-4-ones in good yields. This work
has also demonstrated that spiro association of indane with
4-thiazolidinone containing other nitrogen heterocycles
(1,2,4-triazole and pyridine) showed promising activity
against selected fungi, bacteria, and M. tuberculosis. How-
ever, the nature of the substituent on position-3 of triazole
nucleus, viz. pyridine, 2-methylphenoxy, 4-methylphenoxy,
2,4-dichlorophenoxy, 4-chlorophenoxy, 4-chlorophenyl, and
2,4-dichlorophenyl, is determinant for the nature and extent
of the activity of the synthesized compounds, which might
influence on their mode of actions. Further development of
this group of compounds may lead to compounds with better
antimicrobial and antitubercular profile than standard drugs
by substituting a series of electron donating and heterocyclic
moieties and selectively modifying the spiro system.
Figure 2. Antibacterial activities of synthesized compounds and standard
drug. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
Figure 3. Antifungal activities of synthesized compounds and standard
drug. [Color figure can be viewed in the online issue, which is available
at wileyonlinelibrary.com.]
EXPERIMENTAL
indicates that the incorporation of two or more heterocyclic
moieties in spiro association of indane with thiazolidinone
increases the fungicidal activity of this class of compounds.
Further investigation of these compounds on wider range
of fungi as well as on more dilution is in process.
General
Procedure for one typical case for each step has
been described. Melting points were taken in open capillaries
and are uncorrected. IR spectra were recorded in KBr on a
Shimadzu (Japan) 8201 PC spectrophotometer (nmax in cmꢁ1
)
1
and H-NMR and 13C-NMR spectra in DMSO-d6 on a Bruker
(Switzerland) DRX-300 (300MHz) spectrometer using TMS as a
internal reference (chemical shifts in d, ppm). The purity of
compounds was checked by thin layer chromatography on silica
gel plate using ether, and spots were visualized with iodine
chamber and UV.
Antitubercular activity.
The synthesized compounds
were screened for their antitubercular activity against
Mycobacterium tuberculosis (H37Rv) by Agar microdilution
technique [40]. The results of antitubercular activity were
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Spirothiazolidinones as New Class of Potential Antimicrobial and Antitubercular Agents
General method for the synthesis of 4-amino-3-pyridyl-5-
mercapto-[1,2,4]triazole. This was prepared by the method
(C═C), 1112 (C-N-C); 1H-NMR (DMSO-d6) d: 6.90–7.30
(m, 4H, ph-H), 7.8 (dd, 2H, J= 8.1, ph-H), 7.9 (dd, 2H, J= 8.2, ph-H),
4.81 (s, 2H, -OCH2-), 2.81 (s, 1H, -SH), 2.26 (t, 2H, -CH2), 1.85
(t, 2H, -CH2), 2.13 (s, 3H, CH3); 13C-NMR (DMSO-d6) d: 154.4,
148.4, 147.6, 138.4, 132.5, 132.1, 129.5, 128.9, 128.1, 127.1, 125.4,
124.5, 122.6, 121.4, 65.7, 27.1, 21.3. Anal. Calcd for C19H18N4OS:
C, 65.12; H, 5.18; N, 15.99. Found: C, 65.01; H, 5.06; N, 15.84.
4-(Indan-1-ylideneamino)-3-(2-methylphenoxymethyl)-5-
mercapto-[1,2,4]triazole (1e). Yield, 57%; mp, 138–140 (ꢀC); IR
(KBr, cmꢁ1): 2763 (-SH), 1590 (>C═N), 1559, 1533, 1485
(C═C), 1083 (C-N-C); 1H-NMR (DMSO-d6) d: 6.81–7.43 (m, 8H,
ph-H), 4.89 (s, 2H, -OCH2-), 2.78 (s, 1H, -SH), 2.24 (t, 2H, -CH2),
1.91 (t, 2H, -CH2), 2.24 (s, 3H, CH3); 13C-NMR (DMSO-d6) d:
155.5, 148.2, 146.4, 136.3, 134.4, 132.4, 131.1, 129.9, 128.5, 127.6,
126.5, 125.2, 124.8, 124.1, 123.4, 122.3, 67.2, 26.3, 22.4. Anal.
Calcd for C19H18N4OS: C, 65.12; H, 5.18; N, 15.99. Found: C,
65.04; H, 5.10; N, 15.80.
4-(Indan-1-ylideneamino)-3-(4-nitrophenyl)-5-mercapto-
[1,2,4]triazole (1f ). Yield, 62%; mp, 135–136 (ꢀC); IR (KBr,
cmꢁ1): 2751 (-SH), 1586 (>C═N), 1563, 1529, 1495 (C═C), 1085
(C-N-C); 1H-NMR (DMSO-d6) d: 6.91–7.10 (m, 4H, ph-H), 7.9
(dd, 2H, J = 8.1, ph-H), 8.0 (dd, 2H, J = 8.2, ph-H), 2.99 (s, 1H, -
SH), 2.29 (t, 2H, -CH2), 1.81 (t, 2H, -CH2); 13C-NMR (DMSO-d6)
d: 156.1, 147.3, 146.5, 135.2, 134.9, 133.3, 132.5, 130.4, 128.8,
126.9, 125.4, 124.5, 122.4, 121.8, 120.3, 27.1, 22.1. Anal. Calcd for
C17H13N5O2S: C, 58.11; H, 3.73; N, 19.93. Found: C, 58.02; H,
3.59; N, 19.82.
of Tomayo et al. [41]. Carbon disulfide (2.7 mL, 38.4 mmol)
was slowly added in methanolic solution of appropriate
pyridylacetohydrazine (5 g, 36.5 mmol) and KOH (2.86 g,
36.5 mmol) with constant stirring. This solution was stirred further
for 2–3 h and left overnight. The mixture was then treated with
hydrazine hydrate (2.2 mL, 36.5 mmol) and refluxed for 4 h. The
resulting mixture was cooled and filtered. The filtrate was acidified
with dil. HCl to obtain the triazoles, which were recrystallized from
aq. ethanol. Similarly, the other triazoles were prepared. The
prepared compounds are known and have used for further reaction.
One-pot general method for the synthesis of 2-(3-pyridyl-5-
mercapto-1,2,4-triazol-4-yl)-spiro-(indan-1,2-thiazolidin)4-ones
2a. A mixture of 4-amino-3-pyridyl-5-mercapto-1,2,4-triazole
(1.93 g, 10 mmol), indan-1-one (1.32 g, 10 mmol), and mercap-
toacetic acid (0.77 mL, 7.6 mmol) in polyethylene glycol-400
(15 mL) was heated at 40ꢀC for 5–6 h. The reaction mixture was
poured into ice water and washed with sodium bicarbonate
solution to remove excess of mercaptoacetic acid. The product thus
obtained was filtered, dried, and recrystallized from dioxan : water
(2.40 g, 63%). Similarly, the other compounds were prepared.
Two-step method
General method for the synthesis of 4-(indan-1-ylideneamino)-
3-pyridyl-5-mercapto-[1,2,4]triazoles 1a-1h. 4-Amino-3-pyridyl-
5-mercapto-[1,2,4]-triazole (1.93 g, 10 mmol) and indan-1-one
(1.32 g, 10 mmol) were heated at 40ꢀC in polyethylene glycol
(15 mL) for 5–6 h. The solvent was removed and the reaction
mixture was poured into ice cold water, the crude product thus
obtained was filtered, dried, and recrystallized from dioxan : water
4-(Indan-1-ylideneamino)-3-(4-chlorophenyl)-5-mercapto-
[1,2,4]triazole (1g). Yield, 68%; mp, 193–195 (ꢀC); IR (KBr, cmꢁ1):
2759 (-SH), 1588 (>C═N), 1569, 1523, 1484 (C═C), 1079
1
(C-N-C); H-NMR (DMSO-d6) d: 6.96–7.44 (m, 4H, ph-H), 8.1
(1.98 g, 65%). Similarly, the other compounds were prepared.
(dd, 2H, J= 8.2, ph-H), 8.2 (dd, 2H, J= 8.3, ph-H), 2.94 (s, 1H, -SH),
2.16 (t, 2H, -CH2), 1.79 (t, 2H, -CH2) 13C-NMR (DMSO-d6) d:
156.8, 146.7, 146.1, 136.3, 135.4, 133.6, 133.1, 130.9, 127.4,
125.8, 125.1, 123.9, 123.3 121.4 120.7, 27.9, 23.2. Anal. Calcd
for C17H13ClN4S; C, 59.91; H, 3.84; N, 16.44. Found: C, 59.56;
H, 3.67; N, 16.30.
4-(Indan-1-ylideneamino)-3-pyridyl-5-mercapto-[1,2,4]triazole
(1a). Yield, 65%; mp, 226–229 (ꢀC); IR (KBr, cmꢁ1): 2750 (-SH),
1585 (>C═N), 1558, 1520, 1484 (C═C), 1083 (C-N-C); 1H-NMR
(DMSO-d6) d: 8.01–8.82 (m, 4H, pyridine), 7.21–7.83 (m, 4H, ph-H),
3.09 (s, 1H, -SH), 2.21 (t, 2H, -CH2), 1.83 (t, 2H, -CH2); 13C-NMR
(DMSO-d6) d: 156.4, 149.4, 148.4, 147.2, 146.3, 136.6, 135.4,
133.3, 132.6, 127.1, 125.3, 125.9, 124.4, 121.2, 28.4, 21.2; MS:
m/z 307 (M+). Anal. Calcd for C16H13N5S: C, 62.52; H, 4.26; N,
22.78. Found: C, 62.49; H, 4.16; N, 22.65.
4-(Indan-1-ylideneamino)-3-(2,4-dichlorophenyl)-5-mercapto-
[1,2,4]triazole (1h). Yield, 70%; mp, 105–107 (ꢀC); IR (KBr,
cmꢁ1): 2763 (-SH), 1576 (>C═N), 1551, 1527, 1476
(C═C), 1101 (C-N-C); 1H-NMR (DMSO-d6) d: 6.84–7.65
(m, 7H, ph-H), 2.91 (s, 1H, -SH), 2.21 (t, 2H, -CH2), 1.79
(t, 2H, -CH2); 13C-NMR (DMSO-d6) d: 157.4, 149.8, 146.8,
137.4, 136.8, 136.7, 135.8, 130.7, 128.3, 126.0, 125.9, 125.4,
124.4, 121.9, 120.0, 26.8, 23.5. Anal. Calcd for C17H12Cl2N4S: C,
54.41; H, 3.22; N, 14.93. Found: C, 54.30; H, 3.10; N, 14.69.
General method for the synthesis of 3-(3-pyridyl-5-mercapto-
1,2,4-triazol-4-yl)-spiro-(indan-10,2-thiazolidin)-4-ones 2a-2h. A
mixture of 4-(indan-1-ylideneamino)-3-pyridyl-5-mercapto-[1,2,4]-
triazole 1a (1.54 g, 4.9 mmol) and mercaptoacetic acid (0.38 mL,
5.44 mmol) was heated at 40ꢀC in polyethylene glycol (15 mL) for
5–6 h. The reaction mixture was poured into ice cold water and
washed with sodium bicarbonate solution. The crude product thus
obtained was filtered, dried, and recrystallized from dioxan : water
(1.17 g, 61%). Similarly, the other compounds were prepared.
3-[3-Pyridyl-5-mercapto-1,2,4-triazol-4-yl]-spiro-(indan-10,2-
thiazolidin)-4-one (2a). Yield, 63%; mp, 240–242 (ꢀC); IR
(KBr, cmꢁ1): 2750 (-SH), 1708 (>C═O), 1555, 1511, 1456
(C═C), 703 (C-S-C); 1H-NMR (DMSO-d6) d: 8.01–8.81 (m,
4H, pyridine), 7.21–7.62 (m, 4H, ph-H), 3.91 (s, 2H, -CH2-CO-),
3.01 (s, 1H, -SH), 2.23 (t, 2H, -CH2), 1.79 (t, 2H, -CH2); 13C-NMR
(DMSO-d6) d: 186.4, 158.6, 150.3, 148.1, 145.2, 138.3, 129.4,
4-(Indan-1-ylideneamino)-3-(2,4-dichlorophenoxymethyl)-5-
mercapto-[1,2,4]triazole (1b). Yield, 69%; mp, 116–118 (ꢀC); IR
(KBr, cmꢁ1): 2778 (-SH), 1602 (>C═N), 1540, 1511, 1463 (C═C),
1
1099 (C-N-C); H-NMR (DMSO-d6) d: 7.12–7.81 (m, 7H, ph-H),
5.01 (s, 2H, -OCH2-), 3.02 (s, 1H, -SH), 2.32 (t, 2H, -CH2), 1.84
(t, 2H, -CH2); 13C-NMR (DMSO-d6) d: 154.4, 147.9, 140.2, 138.2,
134.4, 132.2, 131.1, 130.6, 129.4, 128.1, 127.2, 127.9, 126.4,
123.5, 121.2, 66.3, 27.2, 20.3. Anal. Calcd for C18H14Cl2N4OS:
C, 53.34; H, 3.48; N, 13.82. Found: C, 53.16; H, 3.29; N, 13.75.
4-(Indan-1-ylideneamino)-3-(4-chlorophenoxymethyl)-5-
mercapto-[1,2,4]triazole (1c). Yield, 70%; mp, 128–130 (ꢀC); IR
(KBr, cmꢁ1): 2753 (-SH), 1590 (>C═N), 1561, 1526, 1484 (C═C),
1
1103 (C-N-C); H-NMR (DMSO-d6) d: 7.00–7.60 (m, 4H, ph-H),
8.0 (dd, 2H, J = 8.2, ph-H), 8.3 (dd, 2H, J= 8.3, ph-H), 4.91
(s, 2H, -OCH2-), 2.92 (s, 1H, -SH), 2.39 (t, 2H, -CH2), 1.79
(t, 2H, -CH2); 13C-NMR (DMSO-d6) d: 152.3, 149.4, 147.2, 146.2,
133.5, 132.6, 130.4, 130.9, 128.5, 127.9, 126.3, 125.8, 125.1,
123.4, 122.4, 64.5, 26.9, 22.4. Anal. Calcd for C18H15ClN4OS:
C, 58.30; H, 4.08; N, 15.11. Found: C, 58.16; H, 4.01; N, 15.01.
4-(Indan-1-ylideneamino)-3-(4-methylphenoxymethyl)-5-
mercapto-[1,2,4]triazole (1d). Yield, 63%; mp, 121–125 (ꢀC); IR
(KBr, cmꢁ1): 2761 (-SH), 1586 (>C═N), 1559, 1521, 1479
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

S. K. Pandey, A. Ahamd, O. P. Pandey, and K. Nizamuddin
Vol 000
128.2, 127.9, 126.5, 125.9, 124.6, 123.4, 121.1, 68.7, 66.5, 35.2, 27.3;
MS: m/z 381 (M+). Anal. Calcd for C18H15N5OS2: C, 56.67; H, 3.96;
N, 18.36; Found: C, 56.45; H, 3.81; N, 18.25.
140.4, 132.4, 128.0, 127.4, 126.2, 125.9, 125.1, 124.6, 121.3,
120.1, 69.1, 36.8, 31.5, 23.8. Anal. Calcd for C19H15ClN4OS2: C,
55.00; H, 3.64; N, 13.50. Found: C, 54.81; H, 3.51; N, 13.26.
3-[3-(2,4-Dichlorophenyl)-5-mercapto-1,2,4-triazol-4-yl]-spiro-
(indan-10,2-thiazolidin)-4-one (2h). Yield, 64%; mp, 123–125 (ꢀC);
IR (KBr, cmꢁ1): 2774 (-SH), 1714 (>C═O), 1585, 1536, 1461 (C═C),
689 (C-S-C); 1H-NMR (DMSO-d6) d: 6.68–7.63 (m, 7H, ph-H), 3.70
(s, 2H, -CH2-CO-), 2.94 (s, 1H, -SH), 2.24 (t, 2H, -CH2), 1.76
(t, 2H, -CH2); 13C-NMR (DMSO-d6) d: 190.2, 149.9, 148.4, 146.2,
143.2, 138.4, 135.2, 131.8, 131.2, 128.9, 128.4, 127.2, 123.1, 122.1,
120.3, 68.1, 38.5, 36.4, 26.1. Anal. Calcd for C19H14Cl2N4OS2:
C, 50.78; H, 3.14; N, 12.47. Found: C, 50.60; H, 3.10; N, 12.32.
3-[3-(2,4-Dichlorophenoxymethyl)-5-mercapto-1,2,4-triazol-
4-yl]-spiro-(indan-10,2-thiazolidin)-4-one (2b). Yield, 62%; mp,
128–130 (ꢀC); IR (KBr, cmꢁ1): 2761 (-SH), 1710 (>C═O), 1559,
1523, 1461 (C═C), 697 (C-S-C);1H-NMR (DMSO-d6) d: 6.91–7.51
(m, 7H, ph-H), 4.84 (s, 2H, -OCH2-), 3.63 (s, 2H, -CH2-CO-), 2.91
(s, 1H, -SH), 2.19 (t, 2H, -CH2), 1.74 (t, 2H, -CH2); 13C-NMR
(DMSO-d6) d: 189.1, 151.9, 148.4, 141.2 138.6, 133.4, 130.3,
128.8, 128.1, 127.5, 126.4, 125.1, 123.5, 121.8, 121.2, 68.1, 66.2,
38.2, 34.2, 24.3. Anal. Calcd for C20H16N4O2S2Cl2: C, 50.11;
H, 3.36; N, 11.69. Found: C, 49.90; H, 3.26; N, 11.50.
Biological screening
3-[3-(4-Chlorophenoxymethyl)-5-mercapto-1,2,4-triazol-4-yl]-
spiro-(indan-10,2-thiazolidin)-4-one (2c). Yield, 67%; mp, 141–
142 (ꢀC); IR (KBr, cmꢁ1): 2764 (-SH), 1714 (>C═O), 1563,
Antibacterial screening. Preliminary experiments were carried
out to determine the antibacterial activities of spirothiazolidinone
derivatives in vitro against (i) Gram-positive bacteria, S.
pneumoniae and B. subtilis, and (ii) Gram-negative bacteria, E.
coli and P. aeruginosa, by disk diffusion method. The bacterial
strains were subcultured in broth agar and incubated for 18 h at
37ꢀC, and then freshly prepared bacterial cells were spread onto
nutrient agar plate in a laminar flow cabinet. Sterilized paper disks
(6.0mm in diameter) were placed on the nutrient agar plates. Five
milligrams of each test compounds were dissolved in 1 mL of
DMSO separately to prepare stock solution. From stock solution,
different concentrations 50, 25, 12.5, 6.25, and 3.12 mg/mL of each
compound were prepared. Thus, proper amounts of the different
concentrations of compounds were pipetted on the blank disks,
which were placed on the plates. The plates were incubated at 37ꢀC
for 24 h. The MICs, the lowest concentration (mg/mL) of the test
compound that resulted no visible growth on the plate, were
recorded in Table 1. DMSO was used as a solvent control to ensure
that the solvent had no effect on bacterial growth. Ciprofloxacin
was designated in our experiment as a control drug.
Antifungal screening. Titled compounds were screened for their
antifungal activity against C. albicans, A. fumigatus, and A. flavus
(recultured) in DMSO by serial plate dilution method. Test
compound (5 mg) were dissolved in 1 mL of DMSO, and solution
was diluted with water (9 mL). Further progressive dilutions with
melted Mueller–Hinton agar were performed to obtain required
concentrations of 50, 25, 12.5, 6.25, and 3.12 mg/mL. Petri dishes
were inoculated with 1.5 ꢂ 10ꢁ4 colony forming units (CFU) and
incubated at 37ꢀC for 26 h. The MICs in mg/mL were noted. To
ensure that solvent had no effect on fungal growth, a control test
was performed with test medium supplemented with DMSO at the
same dilutions as used in the experiment. Fluconazole was used as
a standard drug.
Antitubercular activity. Drug susceptibility and determination of
MIC of the test compounds/drugs against M. tuberculosis H37Rv were
performed by agar microdilution method where serial twofold
dilutions of each test compound were added into 7H10 agar, and
M. tuberculosis H37Rv was used as test organism. MIC is the
concentration of the compound that completely inhibits the growth
and colony forming ability of M. tuberculosis. In a 24-well plate,
3 mL Middlebrook 7H11 agar medium with OADC supplement is
dispensed in each well. The test compound is added to the
Middlebrook medium agar before in duplicate so that final
concentration of test compound in each well is 12.5, 6.25, 3.12, and
1.56 mg/mL, respectively. The known CFU of H37Rv culture was
dispensed on top of agar in each well in negative pressure biosafety
hood. The plates are then incubated at 37ꢀC/5% CO2 incubator. The
concentration at which complete inhibition of colonies was observed
was taken as MIC of test drug. Isoniazid was used as a standard drug.
1
1510, 1483 (C═C), 701 (C-S-C); H-NMR (DMSO-d6) d: 6.94–
7.69 (m, 4H, ph-H), 8.1 (dd, 2H, J =8.2, ph-H), 8.3 (dd, 2H,
J = 8.3, ph-H), 4.69 (s, 2H, -OCH2-), 3.72 (s, 2H, -CH2-CO-),
2.98 (s, 1H, -SH), 2.23 (t, 2H, -CH2), 1.78 (t, 2H, -CH2);
13C-NMR (DMSO-d6) d: 184.3, 148.3, 146.2, 140.6, 136.4, 135.8,
132.6, 130.9, 126.9, 126.2, 125.2, 121.3, 121.0, 69.8, 66.2, 35.3,
35.1, 24.4. Anal. Calcd for C20H17N4O2S2Cl: C, 53.99; H, 3.85; N,
12.59. Found: C, 53.80; H, 3.79; N, 12.46.
3-[3-(4-Methylphenoxymethyl)-5-mercapto-1,2,4-triazol-4-yl]-
spiro-(indan-10,2-thiazolidin)-4-one (2d). Yield, 61%; mp, 143–
145 (ꢀC); IR (KBr, cmꢁ1): 2770 (-SH), 1701 (>C═O), 1570, 1523,
1469 (C═C), 698 (C-S-C); 1H-NMR (DMSO-d6) d: 6.69–7.44 (m,
4H, ph-H), 7.8 (dd, 2H, J= 8.0, ph-H), 7.9 (dd, 2H, J= 81, ph-H),
4.64 (s, 2H, -OCH2-), 3.81 (s, 2H, -CH2-CO-), 2.99 (s, 1H, -SH),
2.28 (t, 2H, -CH2), 1.81 (t, 2H, -CH2), 2.19 (s, 3H, CH3); 13C-
NMR (DMSO-d6) d: 185.2, 141.9, 139.2, 138.8, 131.2, 130.4,
129.6, 128.7, 124.3, 123.4, 122.8, 122.2, 120.4, 71.2, 64.1, 37.4,
36.1, 25.4, 23.1. Anal. Calcd for C21H20N4O2S2: C, 59.41; H,
4.75; N, 13.20. Found: C, 59.34; H, 4.62; N, 13.11.
3-[3-(2-Methylphenoxymethyl)-5-mercapto-1,2,4-triazol-4-yl]-
spiro-(indan-10,2-thiazolidin)-4-one (2e). Yield, 54%; mp, 180–
183 (ꢀC); IR (KBr, cmꢁ1): 2778 (-SH), 1709 (>C═O), 1564, 1536,
1
1475 (C═C), 691 (C-S-C); H-NMR (DMSO-d6) d: 6.68–7.61 (m,
8H, ph-H), 4.62 (s, 2H, -OCH2-) 3.90 (s, 2H, -CH2-CO-), 2.96 (s,
1H, -SH), 2.21 (t, 2H, -CH2), 1.79 (t, 2H, -CH2), 2.21 (s, 3H, CH3);
13C-NMR (DMSO-d6) d: 190.1, 149.4, 146.1, 144.2, 139.4, 133.2,
130.9, 128.6, 127.9, 127.2, 126.8, 125.4, 124.7, 124.0, 123.7, 68.5,
62.1, 34.6, 31.5, 24.8, 23.2. Anal. Calcd For C21H20N4O2S2: C,
59.41; H, 4.75; N, 13.20. Found: C, 59.32; H, 4.62; N, 13.12.
3-[3-(4-Nitrophenyl)-5-mercapto-1,2,4-triazol-4-yl]-spiro-(indan-
10,2-thiazolidin)-4-one (2f).
Yield, 61%; mp, 158–160 (ꢀC); IR
(KBr, cmꢁ1): 2758 (-SH), 1703 (>C═O), 1570, 1531, 1483
(C═C), 699 (C-S-C); 1H-NMR (DMSO-d6) d: 6.86–7.2 (m, 4H,
ph-H), 7.9 (dd, 2H, J= 8.2, ph-H), 8.0 (dd, 2H, J= 8.1, ph-H), 3.84
(s, 2H, -CH2-CO-), 2.98 (s, 1H, -SH), 2.21 (t, 2H, -CH2), 1.79 (t,
2H, -CH2); 13C-NMR (DMSO-d6) d: 187.3, 150.3, 145.6, 140.2,
131.8, 129.7, 128.4, 127.4, 126.2, 125.2, 124.8, 121.6, 120.3, 68.2,
35.7, 32.6, 24.9. Anal. Calcd for C19H15N5O3S2: C, 53.63; H, 3.55;
N, 16.46; Found: C, 53.46; H, 3.49; N, 16.20.
3-[3-(4-Chlorophenyl)-5-mercapto-1,2,4-triazol-4-yl]-spiro-
(indan-10,2-thiazolidin)-4-one (2g). Yield, 67%; mp, 213–215
(ꢀC); IR (KBr, cmꢁ1): 2769 (-SH), 1710 (>C═O), 1584, 1539,
1475 (C═C), 693 (C-S-C); 1H-NMR (DMSO-d6) d: 6.95–7.44 (m,
4H, ph-H), 8.2 (dd, 2H, J = 8.3, ph-H), 8.3 (dd, 2H, J =8.4, ph-H),
3.79 (s, 2H, -CH2-CO-), 3.01 (s, 1H, -SH), 2.29 (t, 2H, -CH2), 1.80
(t, 2H, -CH2); 13C-NMR (DMSO-d6) d: 189.2, 149.4, 144.1,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014
Spirothiazolidinones as New Class of Potential Antimicrobial and Antitubercular Agents
Acknowledgments. The authors are thankful to the Head of the SAIF,
CDRI for providing IR, 1H-NMR, and 13C-NMR spectral data. The
authors are also grateful to U.G.C., New Delhi, for the financial assis-
tance. The authors are thankful to the Department of Biotechnology,
D.D.U. Gorakhpur University, Gorakhpur, for the help in evaluating
the antibacterial activities.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet